JACKSONVILLE, N.C. – The search for the body of the 20-year-old pregnant Marine believed to have been murdered was suspended Friday evening after authorities found a ditch in the suspect's backyard, according to the North Carolina sheriff handling the case.

Maria Lauterbach had been due to give birth any day, and police have been looking for a fellow Marine she had accused of raping her, according to Onslow County Sheriff Ed Brown.

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The suspect investigators are pursuing is Cpl. Cesar Armando Laurean, 21; the "suspicious cavity" was discovered on the property behind his house.

"It is believed the house and the contents of that cavity may eliminate the need to look any further for the body of missing Marine Maria F. Lauterbach," said the sheriff's office in a statement.

Detectives were combing through Laurean's home Friday night and planned to inspect the contents of the ditch Saturday morning, according to the sheriff.

Lauterbach disappeared nearly a month ago before she was to testify in a military probe and her body was believed to have been buried in a shallow grave in coastal Onslow County, Brown told reporters earlier Friday afternoon.

Lauterbach alleged that she was sexually assaulted by a superior, but that the investigation had gone sour, according to court documents, but authorities had no leads on Laurean's whereabouts.

"They don't know where he is," Brown said. "He's gone."

Laurean, of Clark County, Nev., is driving a black quad cab 2004 Dodge pickup with North Carolina tags and license plate number TRR1522. He joined the Marine Corps in September 2004 and was trained as a personnel clerk. He is listed as Unauthorized Absence status, according to the Marine Corps Base in Camp Lejeune, N.C.

A witness came forward to tell authorities where Lauterbach’s body was buried, Brown said. Brown wouldn't comment on cause of death.

Lauterbach, a lance corporal, made the allegation to her stepmother, who also told investigators that her stepdaughter was bipolar and had a history of compulsive lying, according to the documents filed this week.

The court papers said the anticipated birth of the baby "might provide evidentiary credence to charges she lodged with military authorities that she was sexually assaulted by a senior military person."

Lauterbach's roommate, Marine Sgt. Daniel Durham, isn't a suspect in the case. But authorities believe Durham to be the last person to speak with the missing woman, who may have been monitoring the case while on a training mission in California.

The documents state Naval investigators had struggled to investigate Lauterbach's allegations because of inconsistencies in her account. Still, the court papers said the anticipated birth of the baby "might provide evidentiary credence to charges she lodged with military authorities that she was sexually assaulted by a senior military person."

Lauterbach's stepmother said the fellow Marine threatened the missing woman's career, and search warrants filed this week state the woman was facing a possible discharge from the Marine Corps. No reason was provided.

Lauterbach, originally from Dayton, Ohio, was reported missing Dec. 19 by her stepmother, who last spoke with her five days earlier, authorities said. The Marine's cell phone was found Dec. 20 near the main gate at Camp Lejeune, and she missed a Dec. 26 prenatal-care appointment.

Lauterbach's blue 2006 Hyundai Sonata was found at the Jacksonville Bus Station Monday night. She had purchased a bus ticket to El Paso, Texas, the day after she spoke with her stepmother, but the ticket has not been used, according to the sheriff.

Durham told authorities during an initial interview that he didn't report his roommate as missing because some of her personal items were gone from the residence.

According to court documents, state authorities searched Durham's laptop because they believe the woman may have used it to search for directions on the Internet, as well as her cell phone records and the residence she shared with Durham.

The warrants said a white male tried to use the missing woman's ATM card on Christmas Eve and attempted to cover the ATM's security camera with a rag. Brown declined to say where the card was used.

Mary Lauterbach, the pregnant Marine's mother, said it's not like her daughter not to contact her.

"It's extremely out of character for her not to call home like this," Lauterbach told FOX News. "I'm deeply concerned that something's wrong."

Camp Lejeune officials said the missing woman, who is assigned to the 2nd Marine Logistics Group of the II Marine Expeditionary Force, joined the Marine Corps in June 2006, trained as a personnel clerk and had not deployed to Iraq or Afghanistan.